re: Anyone Have Experience in Buying a Refurbished Mac?

I've never had any problems with refurb devices from Apple.

I'd lean towards the 8gb ram, mostly because the computer will generally last longer use wise and is more adaptable to any potential future use case (can't add more later).

Storage is less important, because worst case you can get usb thumb drives that hold 128gb for fairly cheap, and 13 inch air has sd card slot for more additional storage options if you need more space for stuff later.